I asked this question at the end of another thread, but I think it might get more of a response here. If you have NIK HDR Efex Pro and CS6, I'd like you to try the following:

In the Preferences, on the Interface page, try unchecking "Open Documents As Tabs." close and restart Photoshop and Bridge. Select 3 raw images from an HDR sequence, right-click and select NIK Software>NIK HDR Efex Pro, and see if NIK opens in Photoshop. For me, the procedure goes through all the steps, but after seeing the progress box where the files are aligned I get the following error message: "The command HDR Efex Pro is not currently available."

If I recheck the box, everything goes well. This problem is not seen with PSCS5. I emailed NIK and they had never heard of this, so they could not say whether it is a bug with NIK HDR Efex Pro or CS6 or just my setup.

I'm running the latest versions of CS6 and the NIK software on a WIN7 Ultimate 64-bit machine with an i7 930 processor at 2.8GHz, with 12GB RAM and 1Gb video memory with an up-to-date driver.